CMS is an inflammatory heart disease, primarily affecting farmed Atlantic salmon, Salmo salar L. The disease was first detected in Norway in 1985 and has since been diagnosed in both farmed and wild Atlantic salmon.
CMS is most commonly diagnosed during the late sea-water phase in farmed salmon and is a disease causing considerable losses for the salmon industry. The clinical features of CMS vary from acute death without prior clinical signs to elevated mortality with nonspecific signs such as impaired or abnormal swimming behaviour. Diagnosis of CMS is based on detection of characteristic inflammation and degeneration of spongy myocardium in the atrium and ventricle during histopathological examination.
The causative agent of CMS has been identified as piscine myocarditis virus (PMCV) and the isolation and characterisation of the virus is described in WO 2011/131600.
Methods of controlling the virus are urgently required but despite intensive research, it has not been possible to efficiently culture PMCV, or consequently to produce vaccines based on the attenuated or inactivated virus. Current approaches to vaccinating against CMS are, therefore, based on recombinant PMCV proteins, produced by recombinant expression systems in which no virus is used. Such vaccines, however, do not present the viral proteins in the natural structural context.